Liquids flowing under pressure along a fluid flow line create a "washing" action when their course is diverted. This washing action is exacerbated when the liquids contain abrasive material. It has long been recognized that the washing action severely curtails the useful life of valves which are used to regulate the fluid flow.
Valves experience the most wear on sealing surfaces which are exposed to fluid flow when the valve is in a throttling position. When wear occurs on sealing surfaces leaking occurs.